Low temperature water wash antioxidant solder paste and soldering and water washing methods

Abstract

This invention discloses a low-temperature water-washing antioxidant solder paste, its soldering method, and its water washing method. The solder paste comprises the following components by mass percentage: 89±0.5% Sn42Bi58 solder paste and 11±0.5% flux. The flux comprises, by mass percentage: 2-8% antioxidant, 2-6% stabilizer, 45-55% surfactant, 15-30% solvent, and 10-15% activator. The antioxidant is one or more of benzotriazole, di-tert-butyl-p-cresol, and antioxidant 245. This invention improves the antioxidant performance of the Sn42Bi58 solder paste and reduces oxidation loss during water washing by adjusting the component ratio and adding antioxidants and stabilizers. This solves the problems of antioxidant properties in low-temperature solder paste water washing systems, corrosion of copper by solder paste residue, and soldering ability and operation performance not meeting normal repetitive operation cycles.

Description

Technical Field

[0001] This invention relates to the field of low-temperature solder paste water washing system technology, and in particular to a low-temperature water washing antioxidant solder paste and its soldering and washing methods. Background Technology

[0002] Low-temperature solder paste is a commonly used soldering material in the electronics manufacturing industry, possessing excellent soldering and electrical conductivity. However, during use, low-temperature solder paste is susceptible to oxidation, which reduces its oxidation resistance and reliability. Furthermore, low-temperature solder paste requires rinsing after soldering to remove residual solder paste and prevent negative impacts on electronic components. Therefore, addressing the oxidation issue in the low-temperature solder paste rinsing system and improving product reliability and process stability has become a key focus in the refrigeration industry.

[0003] In existing technologies, several methods have been attempted to address the oxidation resistance issue in low-temperature solder paste washing systems. One approach is to improve the solder paste's oxidation resistance by adjusting the component ratios and adding antioxidants and stabilizers. Another method is to optimize the washing process, adjusting parameters such as washing temperature, time, washing agent concentration, and pH value to improve the washing effect and the ability to remove solder paste residue. Furthermore, employing appropriate drying processes can remove residual moisture during washing, preventing it from negatively impacting the solder paste's oxidation resistance. Auxiliary process steps, such as pretreatment, acid pickling, and deionized water rinsing, can further enhance the washing effect and oxidation resistance. Finally, optimizing solder paste soldering process parameters ensures that soldering capability and operational performance meet normal repetitive operation cycles.

[0004] However, existing technologies have some problems and limitations. For example, while existing solder paste formulation improvement methods can enhance the solder paste's oxidation resistance, they may affect its solderability and handling performance. Optimizing the water washing process also faces challenges in parameter adjustment; excessively high washing temperatures may lead to solder paste oxidation, while excessively low temperatures may fail to completely remove solder paste residue. Simultaneously, the selection and control of the drying process must consider the characteristics of the solder paste and the residual moisture after washing. Furthermore, adding auxiliary process steps may increase production costs and process complexity. Therefore, there is room for improvement in existing technologies, and more effective methods need to be sought to address the oxidation resistance problem of low-temperature solder paste water washing systems. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a low-temperature water-washing antioxidant solder paste and its soldering method and water washing method, so as to solve the antioxidant problem of the low-temperature solder paste water washing system.

[0006] To address the aforementioned technical problems, this invention provides a low-temperature water-washable antioxidant solder paste, comprising the following components by mass percentage: 89±0.5% Sn42Bi58 solder paste and 11±0.5% flux; wherein the flux comprises, by mass percentage: 2-8% antioxidant, 2-6% stabilizer, 45-55% surfactant, 15-30% solvent, and 10-15% activator; the antioxidant is one or more of benzotriazole, di-tert-butyl-p-cresol, and antioxidant 245.

[0007] Furthermore, the stabilizer is one or more of hydroquinone, p-tert-butylcatechol, and monoisooctyl phosphate.

[0008] Furthermore, the surfactant is one or more of the following: tallow amine polyoxyethylene ether, dihydroxyethylamine, fatty alcohol ethoxylate, polyethylene glycol, tetrahydroxypropyl ethylenediamine, hydroxyacetamide, and octadecylamine polyoxyethylene ether.

[0009] Furthermore, the solvent is one or more of diethylene glycol monohexyl ether, tripropylene glycol butyl ether, and terpineol diethylene glycol monobutyl ether.

[0010] Furthermore, the activator is one or more of cyclohexylamine adipate, polyisooctanoate, succinic acid, malic acid, hydroxypropionic acid, and maleic anhydride.

[0011] Accordingly, this embodiment of the invention also provides a soldering method for low-temperature water washing of antioxidant solder paste, wherein the preset time before soldering is 40-60 seconds.

[0012] Accordingly, embodiments of the present invention also provide a method for rinsing antioxidant solder paste with water at low temperature, comprising:

[0013] Water washing steps: During water washing, the water temperature is 45℃, and the pH value of the water washing agent is adjusted to 7.5±0.3. Then, the low-temperature water-washed antioxidant solder paste to be cleaned is washed with water to remove solder paste residue.

[0014] Furthermore, the washing step is followed by a drying step: after washing, the cleaned low-temperature water-washed antioxidant solder paste is dried in an oven or with hot air to remove residual moisture from the washing process, resulting in a completely dry low-temperature water-washed antioxidant solder paste, thus preventing moisture from affecting the antioxidant properties of the low-temperature water-washed antioxidant solder paste.

[0015] Furthermore, in the water washing step, the low-temperature water-washed antioxidant solder paste to be cleaned is pretreated, acid-washed, and rinsed with deionized water in sequence.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. This invention improves the process of low-temperature Sn42Bi58 solder paste in the refrigeration industry. The water washing solution can completely remove solder paste residue, avoid the corrosion of copper materials by solder paste residue, and improve product reliability.

[0018] 2. This invention overcomes the oxidation problem of the low-temperature solder paste water washing system, enabling the water-washed low-temperature Sn42Bi58 solder paste to have oxidation resistance, thereby improving the service life of the solder paste.

[0019] 3. This invention enables the soldering capability and operational performance of water-washed low-temperature Sn42Bi58 solder paste to meet the normal 8-hour repetitive operation cycle, thereby improving production efficiency and product quality. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be further described in detail below with reference to specific embodiments.

[0021] The low-temperature water-washable antioxidant solder paste of this invention comprises the following components by weight percentage: Sn42Bi58 solder paste 89±0.5%, and flux 11±0.5%. The flux is a water-soluble lead-free flux, comprising by weight percentage: antioxidant 2-8%, stabilizer 2-6%, surfactant 45-55%, solvent 15-30%, and activator 10-15%. The antioxidant is one or more of benzotriazole, di-tert-butyl-p-cresol, and antioxidant 245. Practice has shown that the existing antioxidant diethylimidazole, when combined with a diacid, easily produces black oxides in low-temperature solder powder systems, while the combination of this invention better overcomes this problem. The stabilizer is one or more of hydroquinone, p-tert-butylcatechol, and monoisooctyl phosphate. Practice has shown that the existing stabilizers triethanolamine and diethanolamine easily produce black oxides in low-temperature solder powder systems, while the combination of this invention better overcomes this problem. The antioxidants and stabilizers of this invention can improve the antioxidant properties of solder paste and prevent oxidation reactions during water washing.

[0022] Tests showed that the water washing effect of this invention embodiment is as follows: 60% dissolves after soaking in water for 5 minutes, and is completely cleaned after ultrasonic cleaning followed by soaking in water for 1 minute.

[0023] The existing low-temperature water-washable solder paste (Sn42Bi58) has a component ratio of 90±0.5%; antioxidants include one or more of diethylimidazole and benzotriazole at a ratio of 2-8%; and stabilizers include one or more of triethanolamine and diethanolamine at a ratio of 2-6%. Its water-washing effect is as follows: after soaking in water for 5 minutes, there is no significant dissolution; it can be cleaned by ultrasonic cleaning followed by soaking in water for 3 minutes.

[0024] In one embodiment, the surfactant is one or more of tallow amine polyoxyethylene ether, dihydroxyethylamine, fatty alcohol ethoxylate, polyethylene glycol, tetrahydroxypropyl ethylenediamine, hydroxyacetamide, and octadecylamine polyoxyethylene ether.

[0025] As one embodiment, the solvent is one or more of diethylene glycol monohexyl ether, tripropylene glycol butyl ether, and terpineol diethylene glycol monobutyl ether.

[0026] In one embodiment, the activator is one or more of cyclohexylamine adipate, polyisooctanoate, succinic acid, malic acid, hydroxypropionic acid, and maleic anhydride.

[0027] This invention, based on the original method, introduces one or more water-soluble dibasic organic acids such as cyclohexylamine adipate, polyisooctanoate, oxalic acid, and malic acid, along with a surfactant, and adjusts the proportions to improve the antioxidant properties of solder paste. By adding one or more antioxidants such as benzotriazole, di-tert-butyl-p-cresol, and antioxidant 245, and one or more stabilizers such as hydroquinone, p-tert-butylcatechol, and monoisooctyl phosphate, and adjusting the proportions, oxidation losses during the rinsing process can be reduced.

[0028] This invention improves the antioxidant properties of Sn42Bi58 solder paste by adjusting the composition ratio and adding antioxidants and stabilizers, thereby reducing oxidation loss during the water washing process. It solves the problems of antioxidant properties in low-temperature solder paste water washing systems, corrosion of copper materials by solder paste residue, and soldering ability and operation performance that do not meet normal repeated operation cycles. Example 1

[0029] Water-soluble lead-free solder paste consists of the following components in parts by weight:

[0030] 2 parts antioxidant, 26 parts organic solvent, 15 parts activator, 51 parts surfactant, and 6 parts stabilizer.

[0031] The antioxidant is composed of 2-5% di-tert-butyl-p-cresol; the organic solvent is composed of diethylene glycol monobutyl ether and terpineol in a weight ratio of 1:1.6; the activator is composed of malic acid, hydroxypropionic acid, and cyclohexylamine adipate in a weight ratio of 4:5:6; the surfactant is composed of tallow amine polyoxyethylene ether, dihydroxyethylamine, polyethylene glycol 2000, and fatty alcohol ethoxylate in a weight ratio of 16:26:1:8; and the stabilizer is composed of hydroquinone and monoisooctyl phosphate in a weight ratio of 1:1.

[0032] Preparation method of water-soluble lead-free solder paste:

[0033] (1) Mix diethylene glycol monobutyl ether and terpineol in the above proportion as an organic solvent, then prepare the tartrate amine polyoxyethylene ether, dihydroxyethylamine and organic solvent, add them to the reaction vessel and stir to dissolve. The dissolution temperature is 110℃ and the stirring speed is 2000r / min. After it is completely dissolved into a homogeneous, clear and transparent solution, water-soluble rosin is prepared.

[0034] (2) Malic acid, hydroxypropionic acid, cyclohexylamine adipate, hydroquinone and di-tert-butyl-p-cresol were added to water-soluble rosin in sequence for activation and emulsification at a temperature of 88°C, an emulsification rate of 2000 r / min and an emulsification time of 30 min.

[0035] (3) Add fatty alcohol ethoxy compound, polyethylene glycol 2000 and monoisooctyl phosphate to (2) in sequence according to the proportion. The temperature is 78℃ and the rotation speed is 1000r / min. Emulsify for 30 minutes.

[0036] (4) Store at room temperature for 24 hours, then grind the material to a fineness of 15μm, and then refrigerate in a 4℃ freezer for more than 12 hours to ensure the restoration of thixotropy;

[0037] (5) After refrigeration, the mixture is brought back to room temperature to produce a water-soluble lead-free flux.

[0038] Preparation of low-temperature water-washing antioxidant solder paste:

[0039] 11% water-soluble lead-free solder paste and 89% Sn42Bi58 alloy tin powder were placed in a disperser and stirred at a speed of 20 r / min for 10 min. Then, a vacuum was drawn to 0.06 MPa for 10 min while stirring continued. As a result, a low-temperature water-washable antioxidant solder paste with a viscosity of 180±20 Pa·s was obtained. After dispensing, it was sealed and stored at 4℃. Example 2

[0040] Water-soluble lead-free solder paste consists of the following components in parts by weight:

[0041] Antioxidant 4 parts, organic solvent 26 parts, activator 15 parts, surfactant 51 parts, stabilizer 6 parts.

[0042] The antioxidant is composed of di-tert-butyl-p-cresol and benzotriazole in a 1:1 ratio; the organic solvent is composed of diethylene glycol monohexyl ether and 1-decyl alcohol in a weight ratio of 1.6:1; the activator is composed of succinic acid, hydroxypropionic acid, and polyisooctanoate in a weight ratio of 4:5:6; the surfactant is composed of octadecylamine polyoxyethylene ether, tetrahydroxypropyl ethylenediamine, polyethylene glycol 2000, and fatty alcohol ethoxylate in a weight ratio of 16:26:1:8; and the stabilizer is composed of monoisooctyl phosphate and p-tert-butylcatechol in a weight ratio of 1:1.

[0043] Preparation method of water-soluble lead-free solder paste:

[0044] (1) Mix diethylene glycol monohexyl ether and 1-decyl alcohol in the above proportion as an organic solvent, then prepare octadecylamine polyoxyethylene ether, tetrahydroxypropyl ethylenediamine and organic solvent, add to the reaction vessel and stir to dissolve. The dissolution temperature is 110℃ and the stirring speed is 2000r / min. After it is completely dissolved into a homogeneous, clear and transparent solution, water-soluble rosin is prepared.

[0045] (2) Add succinic acid, hydroxypropionic acid, cyclohexylamine adipate, di-tert-butyl-p-cresol, benzotriazole, and p-tert-butylcatechol to water-soluble rosin in sequence for activation and emulsification. The temperature is 88℃, the emulsification rate is 2000r / min, and the emulsification time is 30min.

[0046] (3) Add fatty alcohol ethoxy compound, polyethylene glycol 2000 and monoisooctyl phosphate to (2) in the following order: temperature 78℃, speed 1000r / min, emulsify for 30 minutes.

[0047] (4) Store at room temperature for 24 hours, then grind the material to a fineness of 15μm, and then refrigerate in a 4℃ freezer for more than 12 hours to ensure the restoration of thixotropy;

[0048] (5) After refrigeration, the mixture is brought back to room temperature to produce a water-soluble lead-free flux.

[0049] Preparation of low-temperature water-washing antioxidant solder paste:

[0050] 11% of the water-washed flux prepared in Example 2 and 89% of Sn42Bi58 alloy tin powder were placed in a disperser and stirred at a speed of 20 r / min for 10 min. Then, a vacuum was drawn to 0.06 MPa for 10 min while stirring continued. As a result, a low-temperature water-washed antioxidant solder paste with a viscosity of 180±20 Pa·s was obtained. After dispensing, it was sealed and stored at 4°C. Example 3

[0051] Water-soluble lead-free solder paste consists of the following components in parts by weight:

[0052] Antioxidant 4 parts, organic solvent 26 parts, activator 15 parts, surfactant 51 parts, stabilizer 6 parts.

[0053] The antioxidant is composed of di-tert-butyl-p-cresol and antioxidant 245 in a weight ratio of 1:1; the organic solvent is composed of tripropylene glycol butyl ether and 1-decyl alcohol in a weight ratio of 1.6:1; the activator is composed of maleic anhydride, hydroxypropionic acid, and polyisooctanoate in a weight ratio of 4:5:6; the surfactant is composed of tallow amine polyoxyethylene ether, hydroxyacetamide, polyethylene glycol 2000, and fatty alcohol ethoxylate in a weight ratio of 16:26:1:8; and the stabilizer is composed of monoisooctyl phosphate and hydroquinone in a weight ratio of 1:1.

[0054] Preparation method of water-soluble lead-free solder paste:

[0055] (1) Mix tripropylene glycol butyl ether and 1-decyl alcohol in the above proportion as an organic solvent, then mix tartrate amine polyoxyethylene ether and hydroxyacetamide with the organic solvent, add them to the reaction vessel and stir to dissolve. The dissolution temperature is 100℃ and the stirring speed is 2000r / min. After it is completely dissolved into a homogeneous, clear and transparent solution, water-soluble rosin is prepared.

[0056] (2) Hydroxypropionic acid, succinic acid, polyisooctanoate, di-tert-butyl-p-cresol, antioxidant 245 and hydroquinone were added to the water-soluble rosin in sequence for activation and emulsification. The temperature was 88℃, the emulsification rate was 2000r / min, and the emulsification time was 30min.

[0057] (3) Add fatty alcohol ethoxy compound, polyethylene glycol 2000 and monoisooctyl phosphate to (2) in sequence according to the proportion. The temperature is 78℃ and the rotation speed is 1000r / min. Emulsify for 30 minutes.

[0058] (4) Store at room temperature for 24 hours, then grind the material to a fineness of 15μm, and then refrigerate in a 4℃ freezer for more than 12 hours to ensure the restoration of thixotropy;

[0059] (5) After refrigeration, the mixture is brought back to room temperature to produce a water-soluble lead-free flux.

[0060] Preparation of low-temperature water-washing antioxidant solder paste:

[0061] 11% water-soluble lead-free solder paste and 89% Sn42Bi58 alloy tin powder were placed in a disperser and stirred at a speed of 20 r / min for 10 min. Then, a vacuum was drawn to 0.06 MPa for 10 min while stirring continued. As a result, a low-temperature water-washable antioxidant solder paste with a viscosity of 180±20 Pa·s was obtained. After dispensing, it was sealed and stored at 4℃.

[0062] Comparative Example 1-1

[0063] The difference from Example 1 is that the stabilizer monoisooctyl phosphate is replaced with a triethanolamine component:

[0064] Comparative Examples 1-2

[0065] The difference from Example 1 is that the stabilizer monoisooctyl phosphate is replaced with a diethylimidazole component;

[0066] Comparative Example 2-1

[0067] The difference from Example 2 is that the stabilizer p-tert-butylcatechol was removed;

[0068] Comparative Example 2-2

[0069] The difference from Example 2 is that the surfactant polyisooctanoate is removed;

[0070] Comparative Example 3-1

[0071] The difference from Example 3 is that the antioxidant di-tert-butyl-p-cresol has been removed;

[0072] Comparative Example 3-2

[0073] The difference from Example 3 is that the stabilizer hydroquinone has been removed;

[0074] Example of effect: The performance comparison of the water-washable ultrafine solder paste prepared in Examples 1-5 of the present invention and Comparative Examples 1-6 is shown in Table 1:

[0075]

[0076] Examples 1-3 are all within the scope of protection claimed in this invention. The water-washable solder paste prepared by them has good performance, good stability, high oxidation resistance, no solder beads, no residue or splashing, and a clean water washing effect. It significantly improves the thixotropic index of the solder paste and has a high spread rate.

[0077] Compared to Example 1, Comparative Examples 1-1 and 1-2 both exhibited residual blackening, indicating that the stabilizer and activity matching in Example 1 effectively controlled tin powder oxidation, thereby suppressing residual blackening. Conventional materials triethanolamine and diethylimidazole, however, could not control this phenomenon.

[0078] Compared with Example 2, Comparative Examples 2-1 and 2-2 both showed a large number of tin beads, indicating that the stabilizer has a good synergistic effect on controlling the oxidation of tin powder with both tert-butylcatechol and polyisooctanoate in the activator.

[0079] Compared with Example 3, Comparative Examples 3-1 and 3-2 showed a small amount of tin beads and a large amount of tin beads, respectively, indicating that the antioxidant di-tert-butyl-p-cresol and the stabilizer hydroquinone both had different degrees of synergistic control over the oxidation of tin powder.

[0080] The water washing method for low-temperature water washing of antioxidant solder paste according to an embodiment of the present invention includes the following steps: water washing temperature 45 degrees Celsius; washing time 3 minutes; adjusting the pH value of the water washing agent to 7.5±0.3.

[0081] Testing showed that the cleaning effect was satisfactory, shortening the time and improving efficiency. Compared to existing water washing processes, where ultrasonic cleaning at room temperature for 5 minutes is insufficient, this invention represents a significant improvement.

[0082] In addition, auxiliary process steps such as pretreatment, pickling, and deionized water rinsing can be added during the washing process to further improve the washing effect and antioxidant capacity.

[0083] Drying step: After washing, use an appropriate drying method, such as oven drying or hot air drying, to remove residual moisture from the washing process and prevent moisture from affecting the antioxidant properties of the solder paste.

[0084] The low-temperature water-washing anti-oxidation solder paste soldering method of this invention has a preset time of 40-60 seconds before soldering. According to the water-washing method of this invention, the solder paste soldering process parameters are optimized and adjusted to ensure that the soldering capability and operational performance meet the normal 8-hour repeatable operation cycle.

[0085] Low-temperature water-washed antioxidant solder paste is relatively prone to oxidation. By significantly reducing preheating time and minimizing oxidation loss before reflow soldering, the efficiency of solder paste use and production is improved. The preheating time is reduced from the conventional 60-120 seconds to 40-60 seconds; soldering results are better and production efficiency is higher.

[0086] This invention can overcome the oxidation problem of low-temperature solder paste washing system, and improve product reliability and process stability.

[0087] This invention has good application prospects and market demand.

[0088] Firstly, in the thermoelectric cooler industry, low-temperature Sn42Bi58 solder paste is widely used in the soldering process of thermoelectric coolers. However, traditional water washing processes suffer from oxidation loss and corrosion of copper by solder paste residue, affecting product reliability and process stability. This invention solves these problems and improves product reliability and process stability by improving the solder paste formulation, optimizing the water washing process, adopting appropriate drying processes, adding auxiliary process steps, and optimizing solder paste soldering process parameters.

[0089] Secondly, this invention overcomes the oxidation problem of low-temperature solder paste water washing systems, enabling water-washed low-temperature Sn42Bi58 solder paste to possess oxidation resistance, thereby improving the service life of the solder paste. In the refrigeration industry, product reliability and service life are crucial indicators; therefore, this invention has high application value.

[0090] Furthermore, this invention enables the soldering capability and operational performance of water-washed low-temperature Sn42Bi58 solder paste to meet the normal 8-hour repetitive operation cycle, thereby improving production efficiency and product quality. With the continuous development of the refrigeration chip industry, the requirements for production efficiency and product quality of refrigeration chips are becoming increasingly stringent; therefore, this invention has significant market demand in this field.

[0091] In summary, due to the advanced nature and specificity of this invention, it can be widely applied in fields such as the refrigeration chip industry, meeting the market's demand for reliability, durability, and operational performance of low-temperature solder paste washing systems.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-temperature water-washable antioxidant solder paste, characterized in that, The composition comprises, by weight percentage: 89±0.5% Sn42Bi58 alloy tin powder and 11±0.5% flux; wherein, the flux comprises, by weight percentage: 2-8% antioxidant, 2-6% stabilizer, 45-55% surfactant, 26-30% solvent, and 10-15% activator; the antioxidant is one or more of benzotriazole, di-tert-butyl-p-cresol, and antioxidant 245. The stabilizer consists of hydroquinone and isooctyl phosphate in a weight ratio of 1:1; The surfactant is composed of tallow amine polyoxyethylene ether, dihydroxyethylamine, polyethylene glycol 2000, and fatty alcohol ethoxylate in a weight ratio of 16:26:1:8; The active agent is composed of malic acid, hydroxypropionic acid, and cyclohexylamine adipate in a weight ratio of 4:5:

6.

2. The low-temperature water-washable antioxidant solder paste as described in claim 1, characterized in that, The solvent is one or more of diethylene glycol monohexyl ether, tripropylene glycol butyl ether, and terpineol diethylene glycol monobutyl ether.

3. A method for washing antioxidant solder paste with water at low temperature as described in any one of claims 1-2, characterized in that, include: Water washing steps: During water washing, the water temperature is 45℃, and the pH value of the water washing agent is adjusted to 7.5±0.

3. Then, the low-temperature water-washed antioxidant solder paste to be cleaned is washed with water to remove solder paste residue.

4. The water washing method for low-temperature water washing of antioxidant solder paste as described in claim 3, characterized in that, The washing process is followed by a drying process: after washing, the cleaned low-temperature water-washed antioxidant solder paste is dried in an oven or with hot air to remove any residual moisture from the washing process.

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